1. Field of the Disclosure
The disclosure relates to an apparatus and a method for driving a vacuum pump.
2. Discussion of the Background Art
It is common practice to drive vacuum pump using an electric motor which is supplied with an alternating voltage from a frequency converter via an electric feed line. The frequency converter generates a voltage of variable frequency and/or amplitude for operating the electric motor independently of the frequency and/or amplitude.
Such a frequency converter—also referred to as a drive converter—generates a one- or multi-phase voltage which is variable with regard to voltage and frequency.
Usually, such converters are either supplied with an alternating voltage of 230 V or 400 V, for example, or with a direct voltage of 24 V or 48, for example from voltage supply mains. In the case of supply with an alternating voltage, the latter is rectified and fed to a direct-voltage intermediate circuit of the drive converter. In the case of supply with a direct voltage, the intermediate circuit is directly supplied with the direct voltage. The direct voltage in the intermediate circuit is then converted into a synthetic one- or multi-phase alternating voltage having a variable voltage amplitude and/or frequency and used for supplying the electric motor which drives the vacuum pump. The intermediate circuit voltage and the rated voltage of the electric motor usually have a ratio of approximately 1.5 to 1.
Some vacuum pumps, such as those subjected to a radioactive environment, high temperatures, explosive environments or used in large accelerator plants, for example, must be placed at large distances of 1000 m, for example, from the drive converter since the drive converter is not suitable for operating in radioactive, hot or explosive environments, for example.
At the same time, the pumps must be supplied with a small voltage for reasons of isolation strength (Paschen law), explosion protection and for reason of safety. For example, turbomolecular pumps (TMP) are supplied with 24 V or 48 V.
These small supply voltages necessitate relatively high currents which, in turn, in the case of long feed lines result in increased losses which have to be compensated for. In addition, the feed lines for high currents have a large self-capacitance whose charge must be constantly transferred during operation of the motor. This further increases the value of the currents in the long feed line.
It is an object of the disclosure to reduce the line losses in a vacuum pump drive with a frequency converter arranged at a distance to an electric motor.